The invention relates to apparatus enabling a tubular structure to be connected and locked to an anchor under water. The field of application of the invention is more particularly that of anchoring floating installations for drilling and extracting oil from under water.
In the above field, it is common practice to use surface installations which are fixed to the bottom by means of a plurality of tubular structures (or xe2x80x9clegsxe2x80x9d or xe2x80x9crisersxe2x80x9d) whose bottom ends are locked to anchors which are fixed to the bottom.
For this purpose, it is known to use connection devices comprising connection elements connected respectively to one end of the tubular structure and to the anchor for the purpose of locking the tubular structure to the anchor merely by moving the tubular structure in translation parallel to its axis Such connection devices are described in particular in U.S. Pat. Nos. 4,907,914 and 4,943,188. The connection elements include portions in relief forming guides and co-operating with one another to achieve locking by relative rotation, itself induced by the movement in translation of the tubular structure.
After locking has been achieved and throughout the time the platform is in service, it is necessary to ensure that the tubular structures are capable of pivoting relative to the anchors. This makes it possible accommodate forces acting on the floating installation, e.g. due to currents or to violent winds tending to move it horizontally relative to the bottom. For this purpose, one and/or both of the connection elements can be mounted on hinge means allowing the tubular structure to pivot about a point situated on its axis. The hinge means can be in the form of a ball or a spherical abutment interposed between one of the connection elements and one end of the tubular structure, or between the other connection element and the anchor The hinge means can be constituted by a laminated spherical abutment made up of alternating layers of metal and of elastomer that are bonded to one another, as also described in U.S. Pat. Nos. 4,943,188 and 4,907,914.
With those known apparatuses, difficulties can be encountered when the connection elements are not properly aligned during docking between the tubular structure and the anchor. In the event of mis-alignment, the radial (or horizontal) component exerted during docking can be insufficient or unsuitable for causing the hinge-mounted connection element to pivot into alignment with the other connection element.
The main object of the invention is to resolve the above problem by proposing a connection device whereby a tubular structure and an anchor can be connected together without difficulty even in the event of mis-alignment between the connection elements when they are brought together.
This object is achieved by connection apparatus of the type comprising:
first and second connection elements connected respectively to one end of the tubular structure and to the anchor for locking the tubular structure to the anchor by movement of the tubular structure in translation substantially parallel to its axis; and
hinge means connected to at least one of the connection elements to make it possible, when the tubular structure is connected to the anchor, for the tubular structure to pivot relative to the anchor about a point situated substantially on the axis of the tubular structure;
xe2x80x83in which apparatus;
cables are connected respectively to the tubular structure and to the anchor to enable traction to be exerted on the tubular structure to enable it to be connected to the anchor; and
said cables co-operate with guide means secured to a connection element that is connected to the hinge means such that when the cables are under tension, when traction is applied thereto, they act on said connection element so as to cause it to pivot, where necessary, in order to come into alignment with the other connection element
Thus, the traction of the cables serves not only to move the connection elements towards each other for engagement purposes, but also to bring them automatically into alignment.